It's more about what choice the man has in whether the baby is born.
The woman can choose to terminate or keep the baby, based, apparently, on her bodily autonomy in chosing not to suffer the physical cost that carrying and birthing a baby has on her body.
The man, however, has no say in whether the baby is born or not, even though he can be compelled by a court to support the baby financially until it is 18, suffering the physical cost of doing 18 years of work. (I realise it will not be all of his physical labour over those 18 years, but it is a significant proportion.)
A woman suffers a physical cost when a baby is born, but a man too suffers a physical cost when he is compelled to use his body to work for 18 years in order to support the baby.
Ergo, the woman has bodily autonomy in terms of the baby being born and suffering a physical cost, while the man does not.
CC: @ozimoron